This proposal aims to develop a new generation of high-speed, low-cost, microelectromechanical systems vertical cavity surface emitting lasers (MEMS-VCSELs) for optical coherence tomography (OCT) at multi-MHz axialscan rates. The proposed effort involves a collaboration between Praevium Research, with expertise in MEMS-VCSEL development, and the Massachusetts Institute of Technology (MIT), a leader in OCT system integration and OCT imaging. These ultrahigh speed imaging systems enable new in vivo fundamental and clinical imaging applications, at larger fields of view and finer resolutions than were previously possible. Multi- MHz operation is particularly critical for advancing OCT in cancer studies, which require high speed for large volumeimagingofmicrostructure,anddensesamplingforangiographicimaging(OCTA)andopticalcoherence microscopy(OCM).Theproposedlow-costlaserwillmakethesehighperformancetechnologieswidelyavailable tothefundamentalandclinicalcancerresearchcommunities. PraeviumResearchwillfocusonthedevelopmentofthenewhigh-speed,low-costMEMS-VCSELsweptlaser source. MEMS-VCSELs have recently emerged as a near ideal laser for OCT. These devices offer a unique combination of wide tuning range, high and variable tuning speed, dynamic single mode operation enabling meter-scale imaging range, and the potential for low-cost, enabled by monolithic wafer-scale fabrication and testing.TheproposedworkseekstopushMEMS-VCSELtechnologyto2-5MHzaxialscanratesinamonolithic design,withmultipleapproachestoactuatordesignandpackagingtooptimizelaserspeeds,tuningrange,and sweep linearity. These efforts will significantly reduce manufacturing cost, providing the first volume-scalable, commerciallyavailablesweptsourceformulti-MHzOCT,toenablea10x-40xspeedimprovementoverexisting commercialOCTinstrumentsatafractionofthecostofcurrentsweptsourcetechnologies. MIT will integrate the new light source with state of the art data acquisition and processing and with new endoscopicprobetechnologytodemonstrateinvivoimaginginpatientswithgastrointestinalpathologies.New ultrahighspeedOCTsystemdesignsinvolvinglasersweepmultiplexingandlinearization,andlowlatencyOCT processing and display, will be investigated for performance and feasibility. Micromotor probes, tethered capsules,andpiezoelectricscannerswillbedevelopedforcompactandhigh-precisionopticalimaging.MITwill demonstrate endoscopic applications of these technologies in pre-clinical studies, while investigating system parameters and designs for optimized performance to establish workflow and imaging protocols for potential futureclinicalapplications.InanexistingcollaborationwiththeBostonVeteransAffairsMedicalCenter,MITwill further demonstrate studies in patients with upper and lower gastrointestinal tract pathologies, assessing capabilitiesforwidefieldcoverageofmucosalstructureandvasculature,andcellularmorphology.Theseefforts willmotivatedevelopmentinmanyotherendoscopic,laparoscopic,orsurgicalapplications.